Added clocks tool

cmds/clocks/elems.go

@@ -0,0 +1,13 @@
+package main
+
+import "syscall/js"
+
+func findClockElements(id string) htmlElements {
+	doc := js.Global().Get("document")
+	rootClockElem := doc.Call("querySelector", "#"+id)
+	return htmlElements{
+		locationDiv: rootClockElem.Call("querySelector", ".location"),
+		timeDiv:     rootClockElem.Call("querySelector", ".time"),
+		dateDiv:     rootClockElem.Call("querySelector", ".date"),
+	}
+}

cmds/clocks/main.go

@@ -0,0 +1,87 @@
+//go:build js
+
+package main
+
+import (
+	"log"
+	"time"
+
+	_ "time/tzdata"
+)
+
+func main() {
+	melTime, err := time.LoadLocation("Australia/Melbourne")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	sg, err := time.LoadLocation("Asia/Singapore")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	nyc, err := time.LoadLocation("America/New_York")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	la, err := time.LoadLocation("America/Los_Angeles")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	utc := time.UTC
+
+	clocks := []clock{
+		{
+			name:     "UTC",
+			loc:      utc,
+			elements: findClockElements("utc"),
+		},
+		{
+			name:     "Australia/Melbourne",
+			loc:      melTime,
+			elements: findClockElements("mel"),
+		},
+		{
+			name:     "Asia/Singapore",
+			loc:      sg,
+			elements: findClockElements("sg"),
+		},
+		{
+			name:     "America/New_York",
+			loc:      nyc,
+			elements: findClockElements("nyc"),
+		},
+		{
+			name:     "America/Los_Angeles",
+			loc:      la,
+			elements: findClockElements("la"),
+		},
+	}
+
+	updateClocks(clocks)
+	go startClockUpdater(clocks)
+
+	<-make(chan struct{})
+}
+
+func startClockUpdater(clocks []clock) {
+	for range time.Tick(1 * time.Second) {
+		updateClocks(clocks)
+	}
+}
+
+func updateClocks(clocks []clock) {
+	n := time.Now()
+	for _, c := range clocks {
+		updateClock(n, c)
+	}
+}
+
+func updateClock(t time.Time, clk clock) {
+	lt := t.In(clk.loc)
+	clk.elements.locationDiv.Set("innerText", clk.name)
+	clk.elements.dateDiv.Set("innerText", lt.Format("02 Jan 2006"))
+	clk.elements.timeDiv.Set("innerText", lt.Format("15:04:05"))
+}

cmds/clocks/models.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"syscall/js"
+	"time"
+)
+
+type clock struct {
+	name     string
+	loc      *time.Location
+	elements htmlElements
+}
+
+type htmlElements struct {
+	locationDiv js.Value
+	timeDiv     js.Value
+	dateDiv     js.Value
+}